A331767 - OEIS

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A331767

Number of interior vertices formed by drawing the lines connecting any two of the 2*(n+2) perimeter points of a 3 X (n+1) square grid.

2

7, 29, 89, 201, 387, 641, 1067, 1599, 2305, 3233, 4431, 5855, 7721, 9853, 12369, 15477, 19093, 23141, 28073, 33557, 39699, 46773, 54815, 63681, 73825, 84833, 97005, 110579, 125587, 141733, 160063, 179913, 201105, 224409, 249329, 276215, 305925, 337345, 370793

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Same as A331763, but only count interior crossings.

See A331452 for other illustrations.

LINKS

Lars Blomberg, Table of n, a(n) for n = 1..100

Scott R. Shannon, Colored illustration for a(3) = 89.

CROSSREFS

Cf. A331763, A331765, A331766.

Sequence in context: A242727 A229795 A114043 * A166189 A001779 A257201

Adjacent sequences: A331764 A331765 A331766 * A331768 A331769 A331770

KEYWORD

nonn

AUTHOR

Scott R. Shannon and N. J. A. Sloane, Feb 05 2020

EXTENSIONS

Needs to be extended using the new data for A331763. - N. J. A. Sloane, Mar 12 2020

a(10) and beyond from Lars Blomberg, Apr 28 2020

STATUS

approved